The present invention relates to an ion exchanger.
When a fuel cell is mounted on a vehicle or the like, a cooling circuit that circulates coolant for cooling the fuel cell is provided for the purpose of suppressing temperature rise of the fuel cell at the time of power generation. However, in the cooling circuit, as the concentration of ions contained in the coolant increases due to elution of ions from piping or the like, the electric conductivity of the coolant may be increased. This can degrade the function of the fuel cell. Therefore, the cooling circuit is provided with an ion exchanger for removing ions contained in the coolant (see Japanese Patent No. 4113715). The ion exchanger includes ion-exchange resin, which is formed by blending anion resin and cation resin, and removes ions contained in the coolant through ion exchange in the ion-exchange resin.
Since it is necessary to periodically replace the ion-exchange resin with a new one, the ion exchanger has a structure that allows for easy replacement of the ion-exchange resin. Specifically, the housing of the ion exchanger is provided with an inlet port, through which the coolant in the cooling circuit flows in, and an outlet port, through which the coolant that has flowed into the housing flows out to the cooling circuit. In addition, a cartridge filled with ion-exchange resin is detachably attached to the housing.
When the coolant in the cooling circuit flows into the housing through the inlet port and passes through the ion-exchange resin of the cartridge, ions contained in the coolant are removed through ion exchange in the ion-exchange resin. The coolant after ions are removed in this way flows out from the inside of the housing to the cooling circuit via the outlet port. Also, the replacement of the ion-exchange resin in the above-described ion exchanger is carried out by removing the cartridge together with the ion-exchange resin from the housing, and thereafter attaching another cartridge filled with fresh ion-exchange resin to the housing.
Further, the ion exchanger is provided with a bypass route for causing some of the coolant that has flowed into the housing via the inlet port to flow to the outlet port of the housing while bypassing the ion-exchange resin. The flow area of the coolant in the bypass route affects the flow rate of the coolant passing through the ion-exchange resin. In this respect, the flow area of the coolant in the bypass route is set such that the flow rate of the coolant passing through the ion-exchange resin becomes an optimum value. That is, the flow area of the coolant in the bypass route is determined such that the flow rate of the coolant passing through the ion-exchange resin becomes the optimum value in terms of extending the replacement cycle of the ion-exchange resin and sufficiently removing ions from the coolant.
At the shipment or maintenance of a vehicle, there is a demand for intensive removal of ions from coolant to suppress the concentration of ions contained in the coolant in the cooling circuit below a specified value. To respond to such a demand, a cartridge for intensive ion removal may be employed. Specifically, this cartridge, which is specialized for intensive removal of ions from coolant, is attached to the housing of the ion exchanger at the time of shipment or maintenance of the vehicle. In this state, the coolant is circulated in the cooling circuit.
As an intensive ion removal cartridge, a cartridge is employed that is filled with an optimum amount of ion-exchange resin to intensively remove ions from the coolant, and in which anion resin and cation resin are blended at an optimum ratio for intensively removing ions from the coolant. On the other hand, a cartridge used in normal times (a normal cartridge) is filled with ion-exchange resin the amount of which is optimum for removing ions from the coolant during normal use and that is formed by blending anion resin and cation resin at an optimum ratio for removing ions from the coolant at normal use.
After the concentration of ions in coolant is reduced to a level less than the specified value by intensively removing ions from the coolant by using the intensive ion removal cartridge, the intensive ion removal cartridge is removed from the housing, and a normal cartridge is attached to the housing and used.
However, when the above-described intensive ion removal cartridge is attached to the housing and the coolant in the cooling circuit is circulated, some of the coolant that has flowed into the housing through the inlet port flows into the bypass route in the housing. Then, the coolant that has flowed into the bypass route flows to the outlet port without flowing through the ion-exchange resin, that is, after bypassing the ion-exchange resin. As such, even when a cartridge (ion-exchange resin) specialized for intensive removal of ions from coolant is used, the amount of coolant that flows through the ion-exchange resin of the intensive ion removal cartridge cannot be increased easily. Thus, it is impossible to allow the ion-exchange resin to exert its function to a sufficient extent.
It is conceivable to set the flow area of coolant in the bypass route to be small in consideration of intensive removal of ions from the coolant. In this case, however, when a normal cartridge is used, coolant cannot flow at the optimum flow rate for ion-exchange resin.